United States patent application Ser. No. 08/011,667, filed Jan. 28, 1993, now U.S. Pat. No. 5,361,733, and assigned to the assignee of the present invention, discloses various embodiments of compact valve lifters for internal combustion engines, including some variable valve actuating types, called two-step lifters. These provide two alternative lift curves for actuating a single valve of an engine cylinder to provide variable valve lift and/or timing. Preferably, the lifters have two concentric cylindrical followers actuated by adjacent cams of an associated camshaft and include locking means for connecting the followers together when operating in the extended or high valve lift mode.
United States patent application Ser. No. 08/212,466, filed Mar. 14, 1994 and assigned to the assignee of the present invention, discloses a low mass direct acting valve lifter which includes as a feature a small sized hydraulic element assembly (HEA), or lash adjuster, referred to as a micro HEA. Use of this small HEA in the lifter provides a substantial reduction in the reciprocating mass of the lifter, which can raise valve train speed capability while reducing operating power requirements.